This invention relates to a suspension control system which controls the damping force of a suspension of a vehicle according to travel conditions of the vehicle.
FIG. 5 is a block diagram showing a conventional suspension control system. In FIG. 5, reference numeral 1 designates a suspension control device for controlling the damping force of a suspension; 2, a vehicle speed sensor for measuring a travel speed of a vehicle; 3, a throttle opening sensor for measuring a degree of opening of a throttle valve; and 4, damping force switching means 4 for changing the damping force of the suspension. The vehicle speed sensor 2, the throttle opening sensor 3, and the damping force switching means 4 are connected to the suspension control device 1.
The conventional suspension control system shown in FIG. 5 operates as follows: The suspension control device 1 calculates the acceleration of the vehicle by using a vehicle speed outputted by the vehicle speed sensor 2 and a degree of opening detected by the throttle opening sensor 3. When the acceleration thus calculated is higher than a predetermined value, the suspension control device 1 performs control to increase the damping force of the suspension; that is, it applies a switching instruction to the damping force switching means 4 to increase the damping force of the suspension to minimize variations in posture of the vehicle, thereby to improve the comfortableness in driving the vehicle.
The conventional suspension control device is designed as described above. That is, after the occurrence of acceleration has been detected from variations in the degree of opening of the throttle valve or in vehicle speed, the damping force of the suspension is changed. Hence, it is impossible for the device to prevent the posture of vehicle from changing at the beginning of acceleration or deceleration.
During constant speed travel of the vehicle in which it is essential for the driver to be able to comfortably drive the latter, great variations in posture of the vehicle should be sufficiently suppressed.